1. Field of the Invention
The present invention is generally related to a transmission mechanism for a marine propulsion device and, more particularly, to a system which retains a clutch mechanism in its proper position when a driven shaft is caused to rotate at a speed greater than its associated driving shaft.
2. Description of the Related Art
Those skilled in the art of marine propulsion devices are familiar with many different techniques and structures used to transfer torque from a driving shaft to a driven, or propeller, shaft.
U.S. Pat. No. 3,608,684, which issued to Shimanckas on Sep. 28, 1971, describes a clutch for a marine propulsion device. The device affords reverse operation by rotation of the driveshaft housing about a vertical axis. It includes a clutch in the lower unit gear case for selectively engaging or disengaging the propeller shaft with the driveshaft. The clutch is responsive to axial movement of the driveshaft caused by moving a control handle accessible to the operator.
U.S. Pat. No. 4,223,773, which issued to Croisant et al. on Sep. 23, 1980, discloses a drive engaging apparatus. A clutch apparatus for a marine drive lower gear case includes a propeller shaft rotatably mounted in a gear case housing. A drive gear for both forward and reverse is positioned in the housing coaxial with the propeller shaft and a clutch member is rotatably fixed on the propeller shaft and movable axially into drive engagement with the drive gear. Clutch engaging elements are provided on opposed portions of the drive gears and the clutch member. Shift means utilizing a positive acting cam means positively move the clutch member into and out of engagement from the drive gears. The shift means also include a releasable latch means to positively maintain the shift means in the engaged position and a preloading means between the shift means and the clutch member to snap the clutch member into engagement.
U.S. Pat. No. 4,302,196, which issued to Blanchard on Nov. 24, 1981, describes a marine propulsion unit including propeller shaft thrust transmitting means. The marine propulsion device includes a driveshaft housing mounted for vertical swinging movement about a horizontal axis relative to a boat, a propeller shaft rotatably mounted in the driveshaft housing and having an axis of rotation, and a propeller carried by the propeller shaft. The marine propulsion device also includes a first bevel gear mounted in the driveshaft housing and in coaxial relation to the propeller shaft, a second bevel gear mounted in the driveshaft housing and in coaxial relation to the propeller shaft, and a clutch mechanism for selectively drivingly connecting the bevel gears to the propeller shaft.
U.S. Pat. No. 4,986,774, which issued to Wantz on Jan. 22, 1991, discloses a desmodromic shift adaptor for a counter-rotating propeller shaft assembly. The adaptor member accommodates use of a desmodromic cam-actuated shifting mechanism. The adaptor member includes a cup, which is adapted to mount the fore one of the forward and reverse gears through a bearing member. The adaptor member further includes an internal passage within which is disposed the movable cam of the shifting mechanism, and an opening is in communication with the passage for allowing connection of the shift shaft to the shifting cam after assembly of the adapter member into the gear case cavity.
U.S. Pat. No. 5,449,306, which issued to Nakayasu et al. on Sep. 12, 1995, describes a shifting mechanism for an outboard drive. It provides reduced coupling shock when the forward gears are engaged by a dual clutch assembly, as well as providing for consistent and quick engagement of the clutch assembly with the gear. The shifting mechanism involves a first gear and a corresponding first clutch, and a second gear and a corresponding second clutch. A plunger carries the first and second clutches which are arranged on the plunger at unequal distances from their respective gears.
U.S. Pat. No. 6,112,873, which issued to Prasse et al. on Sep. 5, 2000, describes an anti-backlash dog type clutch. The clutch is provided for mounting on a rotatable shaft. The drive clutch includes a drive gear having a plurality of gear teeth projecting therefrom. A sleeve is slidably mounted on the shaft for rotational movement therewith. The sleeve includes a plurality of gear engaging recesses therein of arcuate lengths greater than the predetermined arcuate lengths of the gear teeth. The sleeve is movable between a first retracted position and a second engaged position wherein the gear teeth are received within corresponding gear engagement recesses in the sleeve in order to translate rotation of the drive gear to the shaft. A plurality of anti-backlash elements are provided to compensate for the difference in the arcuate lengths of the gear teeth and their corresponding gear engagement recesses in the sleeve.
U.S. Pat. No. 6,544,083, which issued to Sawyer et al. on Apr. 8, 2003, discloses a shift mechanism for a marine propulsion system. The mechanism is provided in which a cam structure comprises a protrusion that is shaped to extend into a channel formed in a cam follower structure. The cam follower structure can be provided with first and second channels that allow the protrusion of the cam to be extended into either channel which accommodates both port and starboard shifting mechanisms. The cam surface formed on the protrusion of the cam moves in contact with a selected cam follower surface formed in the selected one of two alternative channels to cause the cam follower to move axially and to cause a clutch member to engage with either a first or second drive gear.
U.S. Pat. No. 6,960,107, which issued to Schaub et al. on Nov. 1, 2005, discloses a marine transmission with a cone clutch used for direct transfer of torque. A transmission for a marine propulsion system uses a cone clutch in such a way that, when in a forward gear position, torque is transmitted from the input shaft, or driving shaft, to an output shaft, or driven shaft, solely through the cone clutch. When in forward gear position, driving torque between the driving and driven shafts is not transmitted through any gear teeth. When in reverse gear position, torque is transmitted through an assembly of bevel gears.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
In certain applications, a driven shaft, such as a propeller shaft, can be caused to rotate faster than an associated driving shaft. Under these conditions, it is possible that a dog clutch member can become disengaged from an associated bevel gear member. It would therefore be significantly beneficial if a system could be provided in which the clutch member is positively retained in meshing relation with the associated bevel gear under these circumstances.